The present invention relates to an air bag device, which operates when impact that is greater than or equal to a predetermined value is applied to the body of, for example, a vehicle, to protect passengers from the impact. More particularly, the present invention relates to a vehicle seat in which a side air bag device is installed.
Such a side air bag device includes an air bag that is inflated between a sidewall of a vehicle body and a passenger who is sitting in a vehicle seat arranged in the vehicle. The side air bag device includes an inflator that discharges inflation gas into the air bag. When the impact applied to the sidewall of the vehicle body is greater than or equal to a predetermined value, the inflator discharges inflation gas to inflate the air bag instantaneously. As a result, the effect of the impact on the passenger is absorbed.
For example, Japanese Laid-Open Patent Publication No. 2000-177527 proposes a side air bag device, which inflates an air bag to the vicinity of a seat surface of a seat. The device especially protects the lumbar region of the passenger in a satisfactory manner and has a superior effect for protecting the passenger.
In the above device, an inflator discharges gas in the direction of the lower end of the air bag, such that the lower portion of the air bag, which corresponds to the lumbar region of the passenger, is inflated quickly.
In this prior art side air bag device, the air bag is required to be inflated to the vicinity of the seat surface. This enlarges the air bag. Accordingly, the inflator must discharge a large amount of inflation gas under high pressure to inflate the air bag quickly.
Additionally, in the device, when an obstacle is placed in the inflation range of the air bag, such as on the surface of the seat, the air bag may be inflated in a state where the obstacle gets caught between the air bag and the seat.
In such a case, during the process in which the air bag is inflated, the inflation gas discharged from the inflator toward the lower end of the air bag impacts the portion where the obstacle is caught in the air bag. Thus, the flow direction of the inflation gas is deflected in an unintended direction. The deflected inflation gas, for example, causes a deviation in the inflation position of the air bag and destabilizes the inflation state of the air bag.